// 设置响应头中间件
module.exports = async (ctx,next)=>{
    const contentType = 'application/json;charset=utf-8'
    ctx.set('Content-Type',contentType)
    ctx.set('Access-Control-Allow-Origin',"*")
    ctx.set('Access-Control-Allow-Methods',"OPTIONS,GET,PUT,POST,DELETE")
    await next()
}